1. Field of the Invention
The present invention relates to a catalytic combustion apparatus, for example, applied to hot water supply and heating for a household or business.
2. Description of the Related Art
Catalytic combustion apparatuses for catalytically combusting fuels using catalyst bodies of noble metal catalysts such as of platinum or palladium carried upon substrates such as cordierite and utilizing the heat generated during combustion for heating have been proposed (for example, Japanese Patent Laid-Open No. Hei6-147419). Such a catalytic combustion apparatus has been equipped with a heat exchange portion upstream of the honeycomb shaped catalyst body for exchanging heat utilizing radiant heat from the catalyst body, and a gaseous mixture of fuel and air has been supplied for catalytic combustion on the catalyst body after heating the catalyst body above its activation temperature for example by flaming the fuel using a spare burner to start catalytic combustion.
However, conventional catalytic combustion apparatuses have problems explained below. First, as the combustion temperature of catalytic combustion is low, in order to increase the amount of heat exchanged the catalyst body must be larger, so that it was difficult to realize downsizing of the apparatus as a whole. When downsizing of the whole apparatus is given up and a large catalyst body is used, stability of combustion tends to be insufficient especially at low combustion quantity, resulting in difficulty of widening of the adjustable combustion quantity range (TDR:Turn Down Ratio). On the other hand, when downsizing was attempted by minimizing the catalyst body, there was a problem that the temperature of the combustion body rose surpassing the limit of heat resistance.
There was also a problem that the method of detecting the condition of combustion based upon ion current in the flame as previously can not be applied, as catalytic combustion is a method of combustion without forming flame.
The present invention is directed to providing a catalytic combustion apparatus that carries out heat exchange more efficiently than previously, taking in consideration the problem of insufficient efficiency of heat exchange in conventional catalytic combustion apparatuses.
The present invention is also directed to providing a catalytic combustion apparatus with wide adjustable combustion quantity range (TDR), taking in consideration the problem that the adjustable combustion quantity range (TDR) was not wide enough in conventional catalytic combustion apparatuses.
The present invention is also directed to providing a downsized compact catalytic combustion apparatus, taking in consideration the problem that conventional catalytic combustion apparatuses were not downsized and compact.
The present invention is also directed to providing a catalytic combustion apparatus in which the catalyst body most upstream does not surpass the limit of heat resistance, taking in consideration the problem that the catalyst body most upstream does surpass the limit of heat resistance in conventional catalytic combustion apparatuses.
The present invention is further directed to providing a catalytic combustion apparatus capable of detecting the condition of combustion, taking in consideration the problem that conventional catalytic combustion apparatuses could not detect the condition of combustion.
In order to solve the problems described above, one aspect of the present invention is a catalytic combustion apparatus which, comprises:
a mixed gas supply portion for mixing fuel with air;
a breathable first catalyst body provided downstream of said mixed gas supply portion;
a breathable second catalyst body provided downstream of said first catalyst body;
a separation board for increasing gas flow resistance, said separation board being provided between said first catalytic body and said second catalyst body;
a heat exchange portion having a heated fluid passage, said heat exchange portion being provided on the peripheral part;and
a radiant heat reception portion connected to said heat exchange portion,
in which said separation board is connected to said heat exchange portion.
Another aspect of the present invention is a catalytic combustion apparatus, which comprises:
a mixed gas supply portion for mixing fuel with air;
a breathable first catalyst body provided downstream of said mixed gas supply portion;
a breathable second catalyst body provided downstream of said first catalyst body;
a heat exchange portion having a heated fluid passage, said heat exchange portion being provided on the peripheral part; and
a radiant heat reception portion connected to said heat exchange portion,
in which gas flow resistance per unit area of said first catalyst body is smaller than gas flow resistance per unit area of said second catalyst body.
Still another aspect of the present invention is a catalytic combustion apparatus, which comprises:
a mixed gas supply portion for mixing fuel with air;
a breathable first catalyst body provided downstream of said mixed gas supply portion;
a breathable second catalyst body provided downstream of said first catalyst body;
a heat exchange portion having a heated fluid passage, said heat exchange portion being provided on the peripheral part; and
a radiant heat reception portion connected to said heat exchange portion,
in which heat exchange coefficient of said first catalyst body is larger than heat exchange coefficient of said second catalyst body.
Yet another aspect of the present invention is a catalytic combustion apparatus, which comprises:
a mixed gas supply portion for mixing fuel with air;
a breathable first catalyst body provided downstream of said mixed gas supply portion;
a breathable second catalyst body provided downstream of said first catalyst body; and
a gas sensor provided between said first catalyst body and said second catalyst body.